It is the aim of this study to translate the findings from preclinical studies to the clinical situation by investigating the feasibility, long-term lead stability and safety of LV septum pacing by transvenous approach through the inter-ventricular septum in patients with a PM or CRT indication. The results may have a large impact on future pacing therapy. The LV septum may become the universal pacing site, being preferred for anti-bradycardia therapy, and being an equal alternative for BiV pacing, but easier to apply, less invasive and more cost-effective.